900 millions worldwide would be great but Avengers final worldwide gross is of something like 888 millions . So I'll say it can earn at least 600 millions worldwide . But who knows , everything is possible

Not likely unless it has WOM on par with Avengers. We will find out soon enough whether that is the case. I put $375m because a $170m opening should lock it for $375m, but there is no guarantee above that. It has a TON of competition coming up over the next month and a half. A lot more competition than IM2 dealt with. A lot more competition than the Avengers dealt with. And it is extremely flawed logic to compare a second sequel with franchise starters in terms of multipliers. Franchise starters are pretty much always less frontloaded than sequels.